Re: [CAD_CAM_EDM_DRO] Router - ballscrew on one end

Yes it will rack. It would take considerable support and mass to eliminate racking driving a gantry from one point. So much so, the gantry would be too heavy for any type of reasonable design.

Moving in the right direction with this approach is long moments of contact on each rail, or at least on the undriven/idling side, the downside to that is a loss in machine travel for that axis. Even then it would be problematic. I'd opt to just use rack and pinion on each side. Or try to find another ballscrew.

I would also reconsider the use of unsupported linear shafting(if it is going to be unsupported). I recall an account by Jon E if I remember it correctly, he had gotten involved with a machine with even large linear shafting as referenced and it still had deflection and vibration problems. Rails have to be supported along their length for machine stiffness. Unsupported rail do not utilize the the strength of the machine base/frame, so it is irrelevant.

That is some unusually large shafting though, A simple test would be take a length of it supported just on the ends and set up a dial indicator and see what it takes to deflect it. Then it's just going to be a judgement call. If it's solid shaft, one problem may be sag due to its own weight.

Ron

vrsculptor <vrsculptor@...> wrote:
I am considering buildings a router with geometry similar to
<http://www.rainnea.com/cnc_5axis.htm> where the x and y axis are on
the top of the machine. I have ballscrews and large (2.5") round
linear ways/bearings to use on the x/y axis. The y axis will have 48"
travel. The machine frame will be steel.

My question is can I drive the X axis from one side of the gantry or
will it bind? I only have 3 ballscrews.

Roger






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